Collect all attributes introduced and redefined in self

Property definitions

nitc :: model_collect $ MClass :: collect_local_mattributes
	# Collect all attributes introduced and redefined in `self`
	fun collect_local_mattributes(filter: nullable ModelFilter): Set[MAttribute] do
		var set = new HashSet[MAttribute]
		set.add_all collect_intro_mattributes(filter)
		set.add_all collect_redef_mattributes(filter)
		return set
	end
src/model/model_collect.nit:847,2--853,4